Treatment of chlorinated isobutane



Dec. 18, 19,34. E. c. BRlTToN Er AL I 1,934,725

TREATMENT OF CHLORINATED ISOBUTANE Filed Dec. 14, 1932 (onder/.ser

fa @wz Vapor* sabu ane as is obtained by i Patented Dec. 18,

The invention relates to a method of hydrolyzing tertiary-butyl chloride. It more particularly concerns a method of working up a mixture conride.

chloro-isobutylenes.

butyl chlorides cannot crystallization methods`V costly for commercial practice. In fractionally distilling the liquid chlorinated mixture the isobutyl and tertiary-butyl together, so that more, if such fractional distillation is carried out in metallic apparatus.

' chlorinated isobutane products (e. g. dichloroisobutanes) is decomposed into hydrogen chloride and chloro-isobutylenes and a considerable portion of the tertiary-butyl chloride usually is decomposed into isobutylene and hydrogen chloride. Still further, the chloro-isobutylenes which are formed during both the chlorination and the distillation steps tend to out the various distillation fractions.

1 In a co-pending application of E. C. Britton,

G. H. Coleman and B. C. Hadler, Serial No. 636.- 996, filed October 10, 1932,-an improved method isobutane is disclosed, whereby the formation of isobutylene and of chloro-isobutylenes is substantially avoided and isobutyl and tertiary-butyl chlorides are formed in high yield, accompanied by'. relatively smallquantities of polychlorinated products. tilling ythe liquid products from such chlorination.

of chlorinating chlorinating isobutane, the method involving the sllective hydroly-sis of the tertiary-butyl chloride in the subsequent separation of the resulting tertiarybutyl alcohol from the unreacted isobutyl chloa complete separation of Vthe isomers is extremely diillcult to attain'. Further- 1.984325 l TREATMENT or cnLoarNA'rr-:n isomerase Edgar C. Britton, Gerald il. Coleman, and Glenn W. Warren, Midland, Mich.. when to The Dow Chemical Company, Midland, Mich., a oorporation of Michigan Application December 14, im, seria Ne. mais zo claims (ci. zee-s) taining isobutyl and tertiary-butyl chlorides, such mixture and the lated by usual methods.

butane mixture con and tertiary-butyl quantities above-mentioned f f separation are too chlorides tend to distill further, metal equipmen a portion of the poly- Conditions' be distributed through- By fractionally'dis- We have now found that a ming isobutyl and tertiarybutyl chlorides can be treated with an aqueous solution or slurry of an alkaline earth metal hydroxide to hydrolyze selectively chloride contained therein without appreciably effecting the isobutyl chloride, tertiary-butyl alcohol can readily be s from the isobutyl chloride and that the so separated compounds can be purified by simple means.

We prefer to employ a c as a khydrolyzing medium in carrying out the selective hydrolysis reaction, although either a calcium hydroxide solution or I a solution or slurry of anyother alkaline earth metal. hydroxide may be used instead.

It is important that the hydrolysis mixture be agitated sufficiently so that the hydrogen chloride, which is produced in the tralized as rapidly as it is formed. o! acid hydrolysis exist within the mixture, a4 portion of the polychlorinated products `(e. g. dichloro-isobutanes) is liable to hydrogen chloride and chloro UNITED s'rA'r's PATENT, OFFICE the distillate is, of course, reduced, but traces of chloro-isobutylenes may be polychlorinated products during such distillation and all of the other diiculties previously mentioned are encountered. Even with such relatively simple chlorinationmixture, then, the monochlorinated products cannot economically be isochlorinated isothe tertiary-butyl that the resulting reaction, is neu- If conditions be decomposed into -isobutylenes and, t in contact with the hydrolysis mixture is liable to be corroded.

of strong alkalinity avoided within the hydrolysis mixture, as the hydrolysis proceeds slowly and decomposition o! tertiary-butyl chloride into isobutylene and hydrosen chloride is liable to occur under such conditions. l.Calcium hydroxide, pensive and but slightly soluble in water, is ideally suited to the purpose and form of a heavy slurry ther conditions o! strong alkalinity solution. Theiollowins description, then, will be directed particularly to the employment of calcium hydroxide as a hydrolyzins agent, but it is to be understood that other alkaline earth metal hydroxides may be employed instead.

'Do the accomplishment ofthe roreg related ends, the invention, then, method hereinafter fully described and lparticuwir pointed out in the claims, the annexed drawshould be being relatively inex- 'can be employed in the eo! without obtaining in the hydrolyzing eparated oin's and consists oi' the formed from the the quantity of chloro-isobutylenes obtained in ing and the followinsv description setting forth in 55 sisting substantially of unreacted isobutane, hy

drogen chloride, isobutyl chloride, tertiary-butyl chloride, and polychlorinated products.

The reacted mixture is passedthrough a cool,--

ing apparatus wherein a considerable-portion of the chlorinated products is condensed and separated and whereinv the residual vapors are'cooled to a temperature below 30 'C. and preferably below 20 C. Hydrogen chloride is then extracted from the residual vapor mixture by scrubbing the latter with water at a temperature below about 30 C. If the temperature materially exceeds 30 C. during such scrubbing operation, a considerable portion of the tertiary-butyl chloride contained in the vapors is liable to be lost through hydrolysis and decomposition thereof. During the scrubbing operation, a smalll quantity of residual chlorinated products may be condensed from the vapors. Such condensed material is separated from the wash water and is combined with the chlorinated products which were condensed during the coolingv operation. The resultant liquid mixture, together with the residual vapor mixture, is passed into a hydrolyzer tted with a distilling column and containingan aqueous solution or slurry of calcium hydroxide.

During hydrolysis, the hydrolyzing medium is agitated and maintained at a temperature between 30 C. andi/00 C., preferably between 30 C. and '70 C., and vapors above said bath pass from the hydrolyzer through the distilling column, which preferably is maintained at such temperature as to obtain an efficient isobutane reflux. The vapors issuing from the distilling column, which consist substantially of unreacted isobutane, are returned to the chlorinator. In order to maintain such isobutane reflux and separate unreacted isobutane effectively from other components of the mixture present in the hydrolyzer, `we prefer to maintain vapors present both in the hydrolyzer and in the ldistilling column under a pressure above about pounds per square inch, gauge. When such mixture is maintained at 20 pounds pressure, gauge, we have found the iso-l butane to reflux efllciently at about C.

After the calcium hydroxide in the hydrolyzing bath is nearly exhausted, the liquid mixture is withdrawn from the hydrolyzer, .filtered to re- -move any solid materials whichmay be present, and the filtrate is passed through a continuous extractorwherein tertiary-butyl alcohol is extracted with water from the isobutyl chloride. In carrying out such extraction, suilcient water should be used so that isobutyl chloride and any' polychlorinated products ,present are renderedA practically insoluble in the aqueous alcohol ex- I tracts.

The aqueous extracts are fractionally distilled to obtain an aqueous tertiary-butyl alcoholcolution, usuallycontaining approximately 86 per cent by weight of tertiary-butyl alcohol. The alcohol product may be dehydrated in anyrof the usual ways, e. g. over calcium oxide or other dehydrat'ing agent, and be distilled to obtain substantially pure tertiary-butyl alcohol. We .have found, however, that the aqueous alcohol can conveniently be dehydrated by dissolving therewith an alkyl chloride (e. g. isobutyl chloride, secondary butyl chloride, propyl chloride, etc.) having a boiling point lower than that of tertiarybutyl alcohol, and distilling a mixture of. the

alkyl chloride and water from the alcohol. Such y alkyl chloride and Water form a relatively low boiling mixture which can be distilled from the tertiary-butyl alcohol to leave the latter in anhydrous and substantially pure form. During such distillation, we prefer continuously to sep- 'arate the aqueous layer of the distillate from the alkyl chloride layer thereof and to recycle the latter 'through the distilling operation until all Water is removed from the alcohol. The aqueous layer of the above distillate usually contains a small quantity of tertiary-butyl alcohol and can veconomically be combined with the crude mixture obtained through hydrolyzing another batch of chlorinated isobutane. The isobutyl chloride -layerfrom which tertiary-butyl alcohol was ex--,4

tracted is fractionally distilled to obtain substantially purev isobutyl chloride.

If either of the above-mentioned distillations are carried out in metal'equipment, it is preferable that an aqueous ,solution or slurry of an alkaline earth metal hydroxidebe present in the distilling mixture. Otherwise, polychlorinated products which may be present are liable to be decomposed into hydrogen chloride and chloroent in said chlorination mixture. The hydrolysis itself is carried out under conditions similar to those already described, i. e. the hydrolyzing mixture is maintained at a temperature between about 30 and 100 C. and is agitated suiiiciently so that conditions of neutral or alkaline hydrolysis are maintained throughout th.J mixture.

Instead of filtering the crude hydrolyzed mixture to separate solids therefrom prior to carrying outthe previously mentioned extraction operation, organic materials can be steam distilled from such hydrolyzed mixture and the distillate can be passed through the extractor.' Again, if desired, tertiary-butyl alcohol can be extracted 'from the crude hydrolyzed mixture without removing solids from the latter, but the extraction can be carriedout more efficiently if no solids are present. .i K

Instead of extracting tertiary-butylV alcohol from the crude hydrolyzed mixture, the latter, which usually contains a small, quantity of unreacted calcium hydroxide, can also be fractionally distilled directly to separate isobutyl chloride and tertiary-butyl alcohol therefrom. When an anhydrous mixture of isobutyl chloride and tertiarybutyl alcohol is fractionally distilled, said -compounds tend to distill together so that va. complete separationci" theiindividual compounds` cannot readily be attained through such procedure. When va mixture containing water, iso- .butyl chloride, and tertiary-butyl'alcohol is fractionally distilled, however, wefhave foundthat the water and isobutyl chloride distill over to-` gether at temperatures considerably below the boiling point of tertiary-butyl alcohol; hence, separation of the organic components of the mixture through such procedure is relatively easy. For reasons previously mentioned, if such,

Example 1 Into a reactor provided with a mechanical stirrer, an inlet for reactants and an efficient distilling column was placed a mixture consisting of '75.8 pounds of calcium hydroxide and 402v pounds of water. The mixture was stirred and maintained at about C. for 1.5 hours, during which period a solution consisting of 172 pounds of tertiary-butyl chloride, 208 pounds of isobutyl chloride, and 20 pounds of isobutylene, was gradually introduced thereto. During the introduction, the reactor and the distilling column were maintained under a pressure of about 10 pounds per square inch, gauge, the distilling column was cooled to about 0 C. with brine, and isobutylene was fractionally distilled from the reaction mixture. After all of the chlorinated hydrocarbon mixture had been passed into the reactor, the liquid hydrolysis mixture was permitted to settle and the aqueous and organic layers thereof were separated. The organic layer was extracted with three successive portions of water, each such portion representing approximately the volume of the organicdayer to be`treated therewith. The aqueous extracts were combined with the aqueous layer of the hydrolysis mixture and the entire solution was fractionally distilled under atmospheric pressure. The fraction distilling over at between 78 and 86 C. was collected and consisted of 141.6 pounds of an aqueous 86 per cent tertiary-butyl alcohol solution. To the organic layer, which had been extracted with water, wasf added 2 pounds of calcium hydroxide and 10 gallons ot water andthe entire rnixturerwas -fractionally distilled to obtain 181 pounds of substantially pure isobutyl chloride.

Example 2V Into a reactor similar to that described in Example 1 were-placed 52 pounds of calcium hydroxide and 202 pounds of water. The mixture was stirred and maintained at 50 C. for 2 hours, during which period a solution of 86.5 pounds of tertiary-butyl chloride, 274 pounds of isobutyl chloride, 20 pounds of polychlorinated hydrocar- \bons, and 20 pounds of isobutane was gradually and-organic layers thereof were separated. lThe organic layer was extracted with three separate portions of water, each such water portion representing approximately the volume of the organic layer to be treated therewith. The aqueous extracts were combined with the aqueous layer of the hydrolysis mixtureand the entire mixture was fractionally distilled under atmospheric pressure to obtain 60.8 pounds of an aqueous 86 per cent tertiary-butyl alcohol solution. 'I'he organic layer which had been extracted with water was mixed with approximately`2pounds of calcium hydroxide and 10 gallons of water and the mixture was fractionally distilled. The following fractions were collectedz-A fraction .distilling over at from 58 to 66 C. containing 232.5 pounds of isobutyl chloride; a fraction distilling over at from 66 to 86 C. containing 13.85 pounds of isobutyl chloride and 13.6 pounds of polychlorinated butanes, and a fraction distilling over at from 86 to 100 C. containing 0.4 pound of isobutyl chloride and 4.6 pounds of polychlorinated butanes.

Example 3 In a reactor provided with a mechanical stirrer, an inlet for reactants, and an eilicient distilling column, were placed '78 pounds of calcium hydroxide and 420 pounds of water. The calcium hydroxide slurry was stirred and maintained at about 50 C. for 1.5 hours, during which period 400 pounds of a chlorinated isobutane solution 'containing 20 pounds of isobutylene, 180 pounds of tertiary-butyl chloride, and 200 pounds of isobutyl chloride was gradually introduced into the reactor at a point below the surface of the stirred through the distilling column. fractions of ldistillate were collected:-(1) a lower fraction distilling over at from 58 to 66 C. containing 165.6 pounds of isobutyl chloride, 18.4 pounds'of tertiary-butyl alcohol, and 3.7 pounds of water; an `intermediate fraction distilling over at from 66 to 76 C. containing 9.2 pounds of isobuty1'chloride, 5.4 pounds of tertiary-butyl al- `cohol, and 0.7 pound of water; and an upper fraction distilling over at from 76 to 86 C. consisting of 120.8 pounds of aqueous 86 per cent tertiarybutyl alcohol.

distillate was con- Atinuously separated and returned tothe still The following The above described procedure may be varied in details without departing from the scope of the invention. For instance, the initial operation of cooling a chlorinated isobutane mixture may be carried out either under a sufficiently'greater pressure, or at a sufficiently lower temperature, or both, than is the subsequent operation of scrubbing hydrogen chloride from the residual vapors with water, so that no chlorinated hydrocarbon products are condensed during said scrubbing operation. Through operating in such manner, the step of separating condensed chlorination products from the scrubbing water is eliminated from the process.

vwise separated from the chlorinated isobutane products' prior to carrying out the hydrolysis operation and the latter. may conveniently be carried out under either atmospheric or superatmospheric pressure.

The foregoing description and examples have been restricted to the employment of a chlorinated lisobutane mixture which initially is substantially free of chloro-isobutylenes. If a chlorinated isobutane mixture which initially contains chloro-isobutylenes is treated according to such procedure, the isobutyl chloride and tertiarybutyl alcohol products may becontaminated with chloro-isobutylenes or unsaturated derivatives thereof, e. g. hydroxy-isobutylene, isobutyraldehyde', etc. Such impurities may be removed from either of said products by treating the latter with a suiiicient quantity of an oxidizing agent, e. g. chlorine, sodium hypochlorite, calcium hypochlorite, potassium permanganate, sodium dichromate, etc., to react with said impurities and thereafter fractionally distilling the mixture in the presence of an aqueous alkaline earth metal hydroxide. As alternative procedure, a chlorinated isobutane mixture containing chloro-isobutylenes can be further chlorinated at a temperature below 200 C. (preferably at or near room temperature) withV suilicient chlorine to react with the chloro-isobutylenes and the resultant mixture 'can then be hydrolyzed and fractionally distilled according to procedure hereintofore described to obtain isobutyl chloride and tertiary-butyl alcohol as substantially the pure compounds.

Our invention is not restricted to the employment of a crude mixture obtained through theV direct chlorination of isobutane. We may em` ploy the present method to obtain isobutyl chloride and tertiary-butyl alcohol lfrom any mixture containing isobutyl and tertiary-butyl chlorides and we have employed the herein-described method to obtain said products from the crude mixture resulting from the thermal molecular rearrangement of substantially pure isobutyl chloride. Further, the step o f hydrolyzing tertiary-butyl chloride and the successive steps of separating tertiary-butyl alcohol from the hydrolyzed mixture can advantageously be employed in producing tertiary-butyl alcohol fromsubstantially pure tertiary-butyl chloride.

'Ifhe present invention, in brief, comprises hydrolyzing l tertiary-butyl chloride with an aqueous alkaline earth metal hydroxide to obtain tertiary-butyl alcohol and the invention more particularly comprises treating a mixture containing isobutyl and tertiary-butyl chlorides with an aqueous alkaline earth metal hydroxide to selectively hydrolyze the tertiary-butyl chloride, and separating bot-h isobutyl chloride and tertiary-butyl alcohol from the hydrolyzed mixture.

Other modes oi applying the principle of our invention may be employed instead of those explained, change being made as regards the method herein explained. provided the step orste'ps stated by any of the following claims o r the equivalent of such stated step or steps be employed.

We therefore particularly point out and distinctly claim as our invention:-

1. The method which comprises reacting tertiary-butyl chloride with an aqueous alkaline earth metal hydroxide to form tertiary-butyl alcohol.

2. The method which comprises reacting tertiary-butyl chloride with aqueous calcium hydroxide at a temperature between about 30 and about 100 C., whereby tertiary-butyl alcohol is formed.

3. The method which comprises treating a mixture containing isobutyl chloride and tertiarybutyl chloride with an aqueous alkaline earth metal hydroxide at a temperature between about 30 and about 100 C., whereby tertiary-butyl A chloride contained in the mixture is selectively hydrolyzed to form tertiary-butyl alcohol.

4. The method which comprises treating a mixture containing isobutyl chloride and tertiary-butyl chloride, at a temperature between about 30 and about 100 C., with a sufficient quantity of aqueous calcium hydroxide to maintain the mixture in alkaline condition during the course ofthe reaction which ensues, and separating isobutyl chloride and tertiary-butyl alcohol from the reacted mixture.

`5. The method which comprises treating a mixture containingrl isobutyl chloride and tertiary-butyl chloride, at a temperature between about and about '10 C., with a sufficient quantity' of aqueous calcium hydroxide to maintain the mixture in alkaline condition during the course of the reaction which ensues, stirring the mixture during the course'of such reaction,- and fractionally distilling the reacted: mixture to separate isobutyl chloride and tertiary-butyl alcohol therefrom. v

6. The method which comprises treating a mixture containing isobutyl chloride and tertiarybutyl chloride, at a temperature between about 30 and about 100 C., with a sufficient quantity of an aqueous alkaline earth metal hydroxide to maintain the mixture in alkaline condition during the course of the reaction which ensues, stirring the mixture during the course of such reaction, and extracting tertiary-butyl alcohol from the water-insoluble components of the reacted mixture with water. l

7. The method which comprises treating a mixturecontaining isobutyl chloride and tertiary-butyl chloride, ata temperature between abouty 30 and about'70 C., with asuiiicient.. quantityI of aqueous calcium hydroxide to maintain the mixture in alkaline condition during the course of the reaction -which ensues, stirring the mixture during the course ofsuch reaction, extracting the reacted mixture with water to separate tertiary-butyl alcohol therefrom, fractionally distilling the aqueous extract to obtain aqueous 'tertiary-butyl alcohol in the form of a relatively pressure and and about 70 C., with'aqueous calcium hydroxide' to maintain the mixture in K ally distilling the aqueous extract to obtain aqueous tertiary-butyl alcohol in a relatively concentrated form, adding to the aqueous tertiary-butyl alcohol an alkyl chloride having a boiling point below that ofsaid alcohol, and fractionally distilling a mixture of water and the alkyl chloride from the tertiary-butyl alcohol to render the iatter substantially anhydrous.

9. The method which comprises treating a mixture containing isobutyl chlori-datertiary-butyl chloride, and a relatively low boiling compound selected from the class consisting of isobutane and isobutylene, under superatmospheric pressure' and at a temperature between about 30 and 100 C., with an aqueous alkaline earth metal hydroxide in amount sufilcient to maintain the mixture in alkaline condition, stirring the mixture during the course of the reaction which ensues, y.and fractionally distilling the above-mentioned relatively low boiling compound from the mixture during the course of such reaction.

10. The method which comprises treating a mixture containing isobutyl chloride, tertiarybutyl chloride, and a relatively low boiling compound selected from the class consisting oi' isobutane and isobutylene, under superatmospheric at a temperature between about in amount suiiicient alkaline condition, stirring the mixture during the course of the reaction which ensues, fractionally distilling the above-mentioned relatively Alow boiling compound from the mixture during the course of said reaction, and separating isobutyl chloride and tertiary-butyl alcohol from the reacted mixture. y y

11. The method which comprises treating a mixture containing isobutyl chloride, tertiary- 'butyl chloride, a aicmoro-isobutane, and a re1- atively low boiling compound selected from the class consisting oi isobutane and isobutylene, under superatmospheric pressure and at a temperature between about 30 and about 70 C.,- withfaqueouslcalcium hydroxide in amount sufiicient to maintain the mixture in alkaline condition, stirring the mixture during the course oi.' the reaction which ensues, fractionally distilling the` above-mentioned relatively low boiling compound from the mixture during the course of said reaction, extracting tertiary-butyl alcohol from the reacted `mixture with water, and fractionally distilling the aqueous extract to obtain aqueous tertiary-butyl alcohol in relatively concentrated form.

butyl chloride,

12. The method which comprises treating a mixture containing isobutyl chloride, tertiarya dichloro-isobutane, a chloroisobutylene, and a relatively low boiling compound selected -from the class consisting of isobutane and isobutylene, under superatmospherlc pressure and at a temperature between about 30 and about 70 C., with aqueous calcium hydroxide in amount sufilcient to maintain the mixture in alkaline condition, stirring the mixture during-the course of the reaction which ensues, fractionally distilling the above-mentioned' relatively low boiling compound from the mixture during the course of said reaction,treating the reacted mixture with a strong oxidizing agent in amount suicient to react withunsaturated compounds present in said mixture, extracting tertiary-butyl alcohol from the mixture with water, rendering the aqueous extract alkaline with an alkaline earth metal hydroxide, and

tween about 30.

calcium hydroxide in amount sufficient to main-4 `kaline earth metal hydroxide,

fractionally distilling aqueous tertiary-butyl a cohol from the resultant alkaline mixture.

13. The method which comprises treating a crude chlorinated isobutane mixture, containing tain the mixture in alkaline condition, stirring the mixture-during the course of the reaction which ensues, fractionally distilling isobutylene and unreacted isobutane from the mixture during the course of said reaction, treating the reacted mixture'with suiiicient chlorine to react with unsaturated compounds present in said mixture, extracting tertiary-butyl alcohol from the mixture with water, rendering the aqueous tertiary-butyl alcohol extract alkaline with analfractionallydistilling the resultant alkaline mixtureto separate a relatively concentrated aqueou" tertiarybutyl alcohol solution therefrom, adding to said relatively concentrated aqueous tertiary-butyl alcohol an alkyl chloride having a boiling point lower than that of tertiary-butyl alcohol, and fractionally distilling a mixture of water and the alkyl "chloride from the alcohol tov render the latter substantially anhydrous.

14. In a method for obtainingisobutyl chlo-` metal hydroxide to maintain the mixture in alkaline condition.

15. In a method for obtaining tertiary-butyl alcohol, the step which consists in distilling aqueous tertiary-butyl alcohol from a mixture containing said compound, a dichloro-isobutane, and a sufficient quantity of an aqueous alkaline earth metal hydroxide to maintain the mixture in alkaline condition.

16. The method of dehydrating aqueous tertiary-butyl alcohol which comprises mixing the same with an alkyl chloride having a boiling point lower than tertiary-butyl alcohol, and fractionally distilling a mixture containing water and said alkyl chloride from the alcohol.

17. The method of dehydrating aqueous tertiary-butyl alcohol which comprises mixing the same with a relatively small quantity of'isobutyl chloride, fractionally distilling a mixture containing water and isobutyl chloride from the alcohol, continuously separating the aqueous layer of the distillate from the isobutyl chloride layer thereof, and continuously recycling the latter through the processuntil the main body of tertiary-butyl alcohol is rendered substantially anhydrous.

18. In a method for obtaining isobutyl chloride, the steps which consist in purifying isobutyl chloride which contains impurities of the class consisting of chloro-isobutylenes and unsaturated hydrolysis and oxidation products of chloroisobutylenes by treating such impure isobutyl chloride with a sufiicient quantity of a strong oxidizing agent to react with the impurities, adding a sufiicient quantity of an aqueous alkaline earth metal hydroxide to render the mixture alkaline, and fractionally distilling isobutyl chloride alcohol, the steps' which consist in purifying tertiary-butyl alcohol which contains impurities of the class consisting of chloro-isobutylenes and unsaturated hydrolysis and oxidation products of chloro-isobutylene, by treating such impure tertiary-butyl alcohol with a suiiicient quantity of a strong oxidizing agent to react with the iin-V purities, adding a suiiicient quantity of an aqueous alkaline earth metal hydroxide to render the mixture alkaline, and distilling aqueous tertiarybutyl alcohol from the alkaline mixture.

20. In a method for obtaining tertiary-butyl alcohol, the steps which consist in purifying tertiary-butyl alcohol which contains impurities of chloro-isobutylene by adding a suicient quantity of an aqueous alkaline earth metal hydroxide to the impure tertiary-butyl alcohol to render the latter alkaline, treating the alkaline mixture with sufficient chlorine to react with the unsaturated impurities contained therein and fractionally distilling aqueous tertiary-butyl alcohol from the chlorinated mixture.

EDGAR C. BRITTONj GERALD H. COLEMAN. GLENN W. WARREN. 

